Make sure rented array is always returned (#49042)

Author: captainsafia

src/Http/Http.Extensions/src/RequestDelegateFactory.cs

@@ -2006,10 +2006,12 @@ private static Expression BindComplexParameterFromFormItem(
 
         return Expression.Block(
             new[] { formArgument, formReader, formDict, formBuffer, formMaxKeyLength },
-            processFormExpr,
-            initializeReaderExpr,
-            Expression.Assign(formArgument, invokeMapMethodExpr),
-            returnBufferExpr,
+            Expression.TryFinally(
+                Expression.Block(
+                    processFormExpr,
+                    initializeReaderExpr,
+                    Expression.Assign(formArgument, invokeMapMethodExpr)),
+                returnBufferExpr),
             formArgument
         );
     }